Re: [PATCH v2] powerpc/mm: export current mmu mode info

[Hari Bathini <hbathini@linux.vnet.ibm.com>]

Hi Michael/Aneesh,

Thanks for reviewing the patch..


On Friday 23 September 2016 04:40 PM, Michael Ellerman wrote:
> Hari Bathini <hbathini@linux.vnet.ibm.com> writes:
>
>> diff --git a/arch/powerpc/include/asm/mmu.h b/arch/powerpc/include/asm/mmu.h
>> index e2fb408..558987c 100644
>> --- a/arch/powerpc/include/asm/mmu.h
>> +++ b/arch/powerpc/include/asm/mmu.h
>> @@ -199,6 +199,21 @@ static inline void mmu_clear_feature(unsigned long feature)
>>   
>>   extern unsigned int __start___mmu_ftr_fixup, __stop___mmu_ftr_fixup;
>>   
>> +/*
>> + * Possible MMU modes
>> + */
>> +#define MMU_MODE_NONE           0
>> +#define MMU_MODE_RADIX          1
>> +#define MMU_MODE_HASH           2
>> +#define MMU_MODE_HASH32         3
>> +#define MMU_MODE_NOHASH         4
>> +#define MMU_MODE_NOHASH32       5
> These are already defined in the same file:
>
> /*
>   * MMU families
>   */
> #define MMU_FTR_HPTE_TABLE		ASM_CONST(0x00000001)
> #define MMU_FTR_TYPE_8xx		ASM_CONST(0x00000002)
> #define MMU_FTR_TYPE_40x		ASM_CONST(0x00000004)
> #define MMU_FTR_TYPE_44x		ASM_CONST(0x00000008)
> #define MMU_FTR_TYPE_FSL_E		ASM_CONST(0x00000010)
> #define MMU_FTR_TYPE_47x		ASM_CONST(0x00000020)
> #define MMU_FTR_TYPE_RADIX		ASM_CONST(0x00000040)
>
> And the values for the current CPU are in cur_cpu_spec->mmu_features.

I primarily tried to introduce this patch as crash tool doesn't have 
access to
offset info (which is needed to access structure member mmu_features) early
in it's initialization process.

> So if you must export anything, make it that value, and hopefully the
> rest of the patch goes away.

On second thought, as long as we can get the vmemmap start address, for 
which
we have a variable already, we can push finding of MMU type for later. I 
may need
no kernel patch in that case. Working on patches for crash & 
makedumpfile tools
accordingly. Will post a v3 only if that doesn't work out..

Thanks
Hari